According to some estimates, billions of people on Earth may have at least a subclinical deficiency of one or another essential chemical element, and therefore, monitoring the elemental status of the population seems a highly important task of modern public nutrition science. The most commonly used biosubstrates for studying elemental composition are blood, urine, and hair. Serum concentrations of chemical elements are subject to the most stringent homeostatic control; thus, serum has the greatest clinical significance but limited preventive value. Whole blood is often used to assess the concentrations of toxic elements, as it combines both serum and cellular components. Urine concentrations are more sensitive to fluctuations in elemental status, which makes them also applicable in preventive medicine. The most suitable biosubstrate for primary screening is hair. Unlike blood and urine, hair analysis allows one to assess the elemental status over a very long period, up to a year. Thanks to this, the analysis of the elemental composition of hair is suitable for extensive research in public health. At the same time, the high lability of hair element concentrations, as well as susceptibility to external contamination, makes this method inapplicable in clinical practice. There are also indirect methods, based on identifying specific markers of a particular element’s deficiency, which makes them much more specific, and as a result, they have the greatest clinical significance, especially when it comes to trace and ultratrace elements. However, so far, the set of such highly specific markers is very limited.